Socy 4156

Whitmeyer

Spring 2008

Study Guide for Test 3 (Chapters 9, 10, 11, 15)

You should be able to:

Decide the appropriate test for the data: 2-sample test for means or proportions, ANOVA, or chi-squared

Say the assumptions we make in conducting a 2-sample test.

Conduct a 2-sample test for means.

Conduct a 2-sample test for proportions.

Know when to use normal (Z-) distribution and t-distribution.

Know how to find critical scores for normal and t-distributions.

Say the assumptions we make in conducting an ANOVA test.

Conduct an ANOVA test.

Say the assumptions we make in conducting a chi-squared test.

Conduct a chi-squared test.

Draw a scatterplot from data.

Calculate predicted values of Y from a bivariate regression equation.

Say what a (y-intercept) and b (slope) in bivariate regression equation mean.

Calculate correlation from data.

Determine whether correlation is significant or not.

Interpret the correlation coefficient.

Explain the difference in meaning between a correlation and an unstandardized regression coefficient.

Interpret the coefficients in a multiple regression table.

For all tests: Know the difference between Type I and Type II error, and which decision runs the risk of which kind of error.

Review Questions:

1. Suppose in a test of the difference between two means, you obtain a t value of 1.911 with 29 degrees of freedom. For the p = 0.05 level the critical value of the t distribution with 29 degrees of freedom is 2.045. What decision do you make and what type of error do you risk?

a) Reject H_o and risk Type I error.

b) Reject H_o and risk Type II error.

c) Fail to reject H_o and risk Type I error.

d) Fail to reject H_o and risk Type II error.

2. Consider the relationship between annual sick days taken and type of job (classified as professional, clerical, and manual). Here are the mean sick days for each job type:

Professional: 4.34 (N=10)

Clerical: 6.14 (N=10)

Manual: 7.91 (N=10)

Here is an ANOVA for these data:

Table: Analysis of Variance of Sick Days by Type of Job

Sum of Mean Sum

Source Squares DF of Squares F

Between Groups 155.750 2 77.875 4.52

Within Groups 465.183 27 17.229

Total 620.933 29

At the p=.05 level, the critical value of the F distribution with 2 and 27 degrees of freedom is 3.35. What do you conclude from these results?

a) These results do not support the hypothesis that for annual sick days taken for different types of jobs, the between-groups and within-groups sums of squares are significantly different.

b) These results do not support the hypothesis that there are significant differences between annual sick days taken for different types of jobs.

c) These results support the hypothesis that there are significant differences between annual sick days taken for different types of jobs.

d) These results support the hypothesis that manual workers take significantly more sick days than do professional and clerical workers.